1 files changed, 78 insertions, 0 deletions
diff --git a/grub-core/kern/i386/tsc.c b/grub-core/kern/i386/tsc.c
new file mode 100644
index 0000000..9293b16
--- /dev/null
+++ b/grub-core/kern/i386/tsc.c
@@ -0,0 +1,78 @@
+/* kern/i386/tsc.c - x86 TSC time source implementation
+ * Requires Pentium or better x86 CPU that supports the RDTSC instruction.
+ * This module calibrates the TSC to real time.
+ *
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2008  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/types.h>
+#include <grub/time.h>
+#include <grub/misc.h>
+#include <grub/i386/tsc.h>
+#include <grub/i386/cpuid.h>
+
+/* This defines the value TSC had at the epoch (that is, when we calibrated it). */
+static grub_uint64_t tsc_boot_time;
+
+/* Calibrated TSC rate.  (In ms per 2^32 ticks) */
+/* We assume that the tick is less than 1 ms and hence this value fits
+   in 32-bit.  */
+grub_uint32_t grub_tsc_rate;
+
+static grub_uint64_t
+grub_tsc_get_time_ms (void)
+{
+  grub_uint64_t a = grub_get_tsc () - tsc_boot_time;
+  grub_uint64_t ah = a >> 32;
+  grub_uint64_t al = a & 0xffffffff;
+
+  return ((al * grub_tsc_rate) >> 32) + ah * grub_tsc_rate;
+}
+
+static int
+calibrate_tsc_hardcode (void)
+{
+  grub_tsc_rate = 5368;/* 800 MHz */
+  return 1;
+}
+
+void
+grub_tsc_init (void)
+{
+  if (!grub_cpu_is_tsc_supported ())
+    {
+#if defined (GRUB_MACHINE_PCBIOS) || defined (GRUB_MACHINE_IEEE1275)
+      grub_install_get_time_ms (grub_rtc_get_time_ms);
+#else
+      grub_fatal ("no TSC found");
+#endif
+      return;
+    }
+
+  tsc_boot_time = grub_get_tsc ();
+
+#if defined (GRUB_MACHINE_XEN) || defined (GRUB_MACHINE_XEN_PVH)
+  (void) (grub_tsc_calibrate_from_xen () || calibrate_tsc_hardcode());
+#elif defined (GRUB_MACHINE_EFI)
+  (void) (grub_tsc_calibrate_from_pmtimer () || grub_tsc_calibrate_from_pit () || grub_tsc_calibrate_from_efi() || calibrate_tsc_hardcode());
+#elif defined (GRUB_MACHINE_COREBOOT)
+  (void) (grub_tsc_calibrate_from_pmtimer () || grub_tsc_calibrate_from_pit () || calibrate_tsc_hardcode());
+#else
+  (void) (grub_tsc_calibrate_from_pit () || calibrate_tsc_hardcode());
+#endif
+  grub_install_get_time_ms (grub_tsc_get_time_ms);
+}